Cell proliferative disorders, such as cancer, are characterized by the uncontrolled growth of cell subpopulations. They are the leading cause of death in the developed world and the second leading cause of death in developing countries, with over 12 million new cancer cases diagnosed and 7 million cancer deaths occurring each year. The National Cancer Institute estimates that greater than half a million Americans will die of cancer in 2013, accounting for nearly one out of every four deaths in the country. As the elderly population has grown, the incidence of cancer has concurrently risen, as the probability of developing cancer is more than two-fold higher after the age of seventy. Cancer care thus represents a significant and ever-increasing societal burden.
Longstanding approaches to cancer treatment include chemotherapy, radiation therapy, and surgery to remove solid tumors. Recently, bispecific antibody-based immunotherapies have been developed. Such bispecific antibodies are capable of simultaneously binding cell surface antigens on cytotoxic cells and tumor cells, with the intent that the bound cytotoxic cell will destroy the bound tumor cell. Existing bispecific antibodies currently undergoing clinical trials for treating cancer are limited by their short half-lives and/or variable efficacy. Thus, there is an unmet need in the field for the development of effective bispecific antibodies for use in cancer treatment.